Development of thermosensitive hydrogel wound dressing containing Acinetobacter baumannii phage against wound infections.

With the emergence of multidrug resistance (MDR) bacteria, wound infection continues to be a challenging problem and represents a considerable healthcare burden. This study aims to evaluate the applicability of a phage loaded thermosensitive hydrogel in managing wound infections caused by MDR Acinetobacter baumannii, using IME-AB2 phage and MDR-AB2 as the model phage and bacteria, respectively. Excellent storage stability of the IME-AB2 phage in a ~18 wt% Poloxamer 407 (P407) hydrogel solution was first demonstrated with negligible titer loss (~0.5 log) in 24 months at 4 °C. The incorporated phage was released in a sustained manner with a cumulative release of 60% in the first 24 h. The in vitro bacterial killing efficiency of phage gel and phage suspension at 37 °C demonstrated >5 log10 CFU/ml reduction against A. baumannii. A comparable biofilm elimination capacity was also noted between the phage gel and phage suspension (59% and 45% respectively). These results suggested that the incorporation of phage into the hydrogel not only had insignificant impacts on the bacterial killing efficiency of phage, but also act as a phage depot to maintain higher phage titer at the infectious site for a prolong period for more effective treatment. We also found that the hydrogel formulation significantly suppressed microbial survival in an ex vivo wound infection model using pig skin (90% reduction in bacterial counts was achieved after 4 h treatment). In summary, our results demonstrated that the P407-based phage-loaded thermosensitive hydrogel is a simple and promising phage formulation for the management of wound infections.